Method of making phthalic anhydride



We Wren.

To all w it may concern:

Be it known that l, l-lmnMATsU Base, of Tokyo, Japan, a Japanese subject, have invented a new and useful Method of Maleing Phthalic Anhydr'ide, of which the following is a specification.

The object of my invention is to efl'ect in a ve efficient manner the production of phtha ic anhydride from nitro-naphthalene.

A further object of my invention is to manufacture phthalic anhydride by the action of sulphuric acid on nitro-naphthalene.

A further object of my invention ,is to furnish a process by which phthalic anhydride may be manufactured economically with ordinary sulphuric acid and a cheap metal such as iron without using mercury or fuming sulphuric acid.

Further objects and features of my invention are hereinafter more particularly set forth in the following description and statement of claims. To my best knowledge phthalic anhydride has been prepared heretofore by oxidizing naphthalene in the presence of mercuric salts with fuming sulphuric acid. The use- 7 of salts or oxides of the rare metals such ascerium, lanthanum, neodymium, praseodymium, and ytterbium, has been proposed instead of mercur But I am not aware that it has been trie to produce phthalic anhydride from nitro-naphthalene instead of naphthalene using such a metal as iron or zinc instead of mercury.

Tn my invention p thalic anhydride is preparedby treating nitro-naphthalene with sulphuric acid in the presence of iron or other suitable metal, which may be used for Such naphthalene produced as above is I directly oxldized with sulphuric acid as soon as it is produced and thus phthalic anhydride'is produ by the following equation:

Tn the process of my invention, phthalic Application med 0eteber all, 1010. aerial file. name.

the reduction of nitro-eompounde. The,

process of treatment of my invention is a llows:

In a suitable vessel, o lrilos of ordinary sulphuric acid of 65 11 are heated to 150-160 U, and then 35 kilos of nitronaphthalene is added. The latter is then fused into the sulphuric acid, after which from 80 to 90 lrilos of iron borings or zinc dust are added thereto under agitation. The reaction is very vigorous, all gases such as sulphur dioxide, carbon dioxide, etc, bemg allowed to escape. A temperature of 200 C. is maintained until all such. gases are driven oil". The tern erature is then raised about 300 C. and p thalic anhydride is driven off and recovered by condensation under proper sub-atmospheric pressure.

The reason why the process of my invenilon produces phthalic anhydride is as folows:

When nitro-naphthalene is reduced according to the ordinary process, naphthylamine is produced by the following equat1on:'

In the process of my invention, hower, 1t 1s reduced to naphthalene instead of naphthylamine on account of its vigorous equation anhydride canbe easily produced with orditill all

till

nary sulphuric acid but more concentrated sulphuric acid or fuming sulphuric acid maybe used for the purpose to procure better yield. 1 i

Havin now particularly described the nature 0 my said invention and in what manner the same is to be perfoed, what I claim is:--

1. The .process of producing phthalic anhydride which consists in can sulphuric acid to be heated to below 160 0., and

acid to act onnitronaphthalene at a tem- 1t perature of apfroximately 200." C. until reaction is 00mg) etc, then increasing the temperature of-t e remaining reaction roduct,

'and'volatilizing the phthalic anhy ride out of said product and condensing the same.

In testimony, that I claim the foregoing as my invention, I have signed my name in the presence .of two subscribing witn.

HIDEMATSU SASA. a a] Witnesses Smomosm SAKABE, KANAE Mono. 

